Study of arc stability in underwater shielded metal arc welding at shallow depths

2008 ◽  
Vol 223 (3) ◽  
pp. 699-709 ◽  
Author(s):  
J A E Mazzaferro ◽  
I G Machado
Keyword(s):  
Weld Metal ◽  
Fourier Transforms ◽  
Short Circuit ◽  
Welding Current ◽  
Shielded Metal Arc Welding ◽  
Metal Quality ◽  
Electrode Coating ◽  
Welding Condition ◽  
Porosity Level ◽  
Arc Stability

The main objective of this work was to study the effects of changes in hydrostatic pressure and electrode coating composition on the shielding metal arc behaviour during underwater wet welding. Thus, wet welding operations were performed by an automatic device using a hyperbaric chamber to simulate depths of 5.0, 12.5, and 20.0 m. A covered electrode already developed in W & RTL was used as reference and compared with others with different amounts of CaCO3, TiO2, and aluminium added to their coatings. Hence, effects of welding condition and electrode coating on weld metal were evaluated through visual inspection of the weld beads, measurement of porosity level, and the results related to welding current and voltage signals. The welding arc signals were analysed through indexes calculated from instantaneous values of current and voltage, and fast Fourier transforms frequency spectrum. The mixtures containing CaCO3 additions exhibit fewer defects, while those containing aluminium additions have presented a great amount of pores and other discontinuities in the weld metal. As expected, all consumables showed a higher deposition rate, as welds were performed at greater depths (pressures), confirming the effect of arc constriction and the consequent increase in current density. Moreover, a region of transition in the metal transfer mode was identified around a depth of 12.5 m, probably from short-circuit to globular. Also, a clear tendency of increase in arc stability for those welds performed at greater depths could be noticed, as well as better weld metal quality. On the other hand, those consumables with CaCO3 added to the coating exhibited the best arc stability for welds performed at shallow depths.

Effect of Electrode Coatings on Diffusible Hydrogen Content, Hardness and Microstructures of the Ferritic Heat Affected Zones in Bimetallic Welds

2011 ◽  
Vol 383-390 ◽  
pp. 4697-4701 ◽  
Author(s):  
Deepak Bhandari ◽  
Rahul Chhibber ◽  
Navneet Arora
Keyword(s):  
Weld Metal ◽  
Nuclear Power ◽  
Power Plants ◽  
Welding Process ◽  
The Other ◽  
Scientific Development ◽  
Shielded Metal Arc Welding ◽  
Diffusible Hydrogen ◽  
Metal Quality ◽  
Welding Electrode

Bimetallic welds (BMWs) have been a necessity within the steam generators of nuclear power plants, where the heavy section low alloy steel components are usually connected to stainless steel primary piping systems. These welds represent zones with metallurgical discontinuities, which tend to localize the strains and cause failures. The other critical issues which must be taken care of while welding of bimetallic joints include solidification cracking, thermal fatigue and residual stresses in welds. The occurrence and severity of all these problems associated with bimetallic welds depend upon the type of welding process used along with the other variables like welding consumables, heat input etc. In shielded metal arc welding (SMAW), welding electrode consumables/coatings play an important role in deciding the weld metal quality. The development of welding electrode coatings is quite difficult due to very rapid complex reactions taking place during welding and the involvement of many controlled process variables. The present paper is an effort to highlight the general issues and challenges for the systematic and scientific development of welding electrode coatings for bimetallic welds. The experimental procedure contains three sets of coated electrodes having varying ferro-alloys, silica and carbon content. In the first set of electrodes, non-ferrous elements are also introduced into the weld metal through flux addition. Further, the welded joints are subjected to various tests and then evaluated to ascertain their mechanical as well as metallurgical behaviour.

Weld Metal Chemistry of Mineral Waste Added SiO2–CaO–CaF2–TiO2 Electrode Coatings for Offshore Welds

2020 ◽  
Vol 142 (3) ◽  
Author(s):  
Waris Nawaz Khan ◽  
Rahul Chhibber
Keyword(s):  
Weld Metal ◽  
Structural Integrity ◽  
Offshore Structures ◽  
Tio2 Electrode ◽  
Shielded Metal Arc Welding ◽  
Electrode Coating ◽  
Metal Chemistry ◽  
Metal Arc Welding ◽  
Welding Consumables ◽  
Mineral Waste

Abstract Offshore structures in recent time are witnessing the increased application of dissimilar metal welds for enhanced structural integrity. Offshore structures are complex systems. Fabrication, maintenance, and repair of these structures require conventional and advanced welding technologies along with suitably chosen welding consumables. The present work aims at the design and development of shielded metal arc welding (SMAW) electrode coating using extreme vertices design methodology. This work also attempts to study weld metal chemistry along with microstructure and microhardness. Red ochre, a mineral waste from iron ore is added in the coating composition. Multi response optimization has been carried out to obtain optimum flux composition and to study the effect of individual constituents and their interactions on the weld chemistry and microhardness.

SMAW Electrodes Selection for Producing Hard-Faced Layer on FC25 Cast Iron Surface

2018 ◽  
Vol 777 ◽  
pp. 339-343
Author(s):  
Pramote Poonayom ◽  
Kittipong Kimapong
Keyword(s):  
Cast Iron ◽  
Impact Strength ◽  
Weld Metal ◽  
Welding Current ◽  
Welding Parameters ◽  
Alloying Element ◽  
Shielded Metal Arc Welding ◽  
Metal Arc Welding ◽  
Covered Electrodes ◽  
Selection For

A shielded metal arc welding (SMAW) using various covered electrodes applied to produce a hard-faced weld metal on FC25 gray cast iron bare surface. It found that all welding parameters such as 3 electrode types and welding currents of 90-130 A were able to produce a sound weld metal without a defect that could deteriorate the joint strength. The white cast layer thickness that was formed at the interface between the weld metal and the base metal was increased when increasing in the welding current and the alloying element in the electrode. Impact strength tended to increase when the alloying element such as chromium (Cr), molybdenum (Mo), and manganese (Mn) was existed, and it showed the maximum impact strength when H600 electrode was applied. In a comparison of microstructure characteristics of the joints, the joint that showed the maximum impact strength had the formation of fine needle-like grain in the weld.

Effect of Welding Consumables on Dissimilar AISI304/AISI1015 Steels Butt Joint Properties

2018 ◽  
Vol 777 ◽  
pp. 344-349
Author(s):  
Surat Triwanapong ◽  
Kittipong Kimapong
Keyword(s):  
Impact Strength ◽  
Weld Metal ◽  
Welding Current ◽  
Interface Structure ◽  
Butt Joint ◽  
Shielded Metal Arc Welding ◽  
Metal Arc Welding ◽  
Joint Properties ◽  
Covered Electrodes ◽  
The Impact

The butt joint of dissimilar AISI304/AISI1015 steels was produced by a Shielded Metal Arc Welding (SMAW) with 3 types of the covered electrodes and the welding current of 80-120 A. The investigation of joint properties for the impact strength, the hardness, and the microstructure, was performed. The SMAW butt joint that was welded by the E312 covered electrode and 100A welding current showed the highest impact strength of 112 J. The chromium was the important reinforced element affected to increase in the hardness and the impact strength of the joint by forming and dispersing the chromium carbide in the weld metals. Interface structure of the carbon steel/the weld metal clearly showed a small combined area of the metals in opposition to the interface structure of the stainless steel/ the weld metal which had a large combined area of the metals.

Combining CaO–SiO2–TiO2 and CaO–SiO2–Al2O3 ternary phase systems for design of bimetallic welds

2021 ◽  
Vol 235 (8) ◽  
pp. 1271-1283
Author(s):  
Deepak Bhandari ◽  
Rahul Chhibber ◽  
Lochan Sharma ◽  
Navneet Arora ◽  
Rajeev Mehta
Keyword(s):  
Weld Metal ◽  
Power Plants ◽  
Ternary Phase ◽  
Desirability Function ◽  
Manganese Content ◽  
Research Work ◽  
Welding Process ◽  
Delta Ferrite ◽  
Electrode Coating ◽  
Phase Systems

The bimetallic welds are frequently utilized for pipeline transport system of the nuclear power plants. The occurrences of welding defects generally depend on the filler electrode as well as the electrode coatings during shielded metal arc welding process. This study involves the design of austenitic stainless steel welding electrodes for SS304L–SA516 bimetallic welds. The objective of research work includes the novel design of Al2O3–TiO2–CaO–SiO2 coatings by combining two ternary phase systems using extreme vertices mixture design methodology to analyze the effect of key coating constituents on the weld metal chemistry and mechanical properties of the welds. The significant effect of electrode coating constituent CaO on weld metal manganese content is observed which further improves the toughness of bimetallic weld joints. Various regression models have been developed for the weld responses and multi objective optimisation approach using composite desirability function has been adopted for identifying the optimized set of electrode coating compositions. The role of delta ferrite content in promoting the favourable solidification mode has been studied through microstructural examination.

Experimental investigation on dissimilar weld between super duplex stainless steel 2507 and API X70 pipeline steel

2021 ◽  
pp. 146442072110130
Author(s):  
Waris N Khan ◽  
Rahul Chhibber
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Pipeline Steel ◽  
High Strength ◽  
Super Duplex Stainless Steel ◽  
Shielded Metal Arc Welding ◽  
Electrode Coating ◽  
Dissimilar Weld ◽  
Metal Arc Welding ◽  
Welding Electrode

This work investigates the microstructure and mechanical properties of 2507 super duplex stainless steel and API X70 high strength low alloy steel weld joint. This joint finds application in offshore hydrocarbon drilling riser and oil–gas pipelines. Coated shielded metal arc welding electrodes have been designed and extruded on 309L filler and their performance compared with a commercial austenitic electrode E309L. Filler 309L solidifies in ferrite-austenite (F-A) mode with a resultant microstructure comprising skeletal ferrites with austenite distributed in the interdendritic region. Results of tensile and impact tests indicate that weld fabricated with laboratory-developed electrodes has higher ductility and impact energy than the commercial electrode. The tensile strength and weld hardness of commercial electrodes are superior. The laboratory-made electrode’s microhardness is lower than the commercial electrodes, making the former less prone to failure. An alternative welding electrode coating composition has been suggested through this work and found to be performing satisfactorily and comparable to the commercially available electrodes.

Predicting Bead Geometry of 2F-Fillet Joint Welded by Small Wire SAW

2012 ◽  
Vol 576 ◽  
pp. 185-188 ◽  
Author(s):  
Shahfuan Hanif Ahmad Hamidi ◽  
Abdul Ghalib Tham ◽  
Yupiter H.P. Manurung ◽  
Sunhaji Kiyai Abas
Keyword(s):  
Welding Current ◽  
Weld Bead ◽  
Welding Parameter ◽  
Bead Geometry ◽  
Weld Bead Geometry ◽  
Absolute Deviation ◽  
Fillet Weld ◽  
Welding Condition ◽  
Code Of Practice ◽  
The Cost

The cost of development of WPS will be very expensive if the welding parameter is selected based on trial and error. Optimal welding condition cannot be easily guessed unless the operator has records of good welding. If a calculator that can predict the welding parameter for the desired bead geometry accurately, such tool will be extremely useful for any fabrication industry. This paper intends to investigate the correlation between the welding parameter and weld bead geometry of 2F position T-fillet carbon steel, when welded by 1.2 mm diameter wire submerged arc welding. Keeping only one parameter as variable, 2F fillet weld coupons are welded by SAW with a range of welding current, welding voltage and welding speed. Only weld bead geometry that complied with the quality requirement of code of practice AWS D1.1 is considered. The trendline graph is created to fit the correlation between the heat input and the fillet weld geometry. By incorporating the trendline formulas into the calculator, the weld bead geometry can be predicted accurately for any welding parameter. The mean absolute deviation (MAD) between the predicted geometry and the experimental results is less than 0.50mm.

scholarly journals Effects of robotic CO2 arc welding variables on penetration and microstructure of weld in C-80 grade steel

2010 ◽  
Vol 7 (1) ◽  
pp. 67-75
Author(s):  
Hamid Reza Ghazvinloo ◽  
Abbas Honarbakhsh-Raouf ◽  
Nasim Shadfar
Keyword(s):  
Weld Metal ◽  
Cross Sections ◽  
Arc Welding ◽  
Welding Process ◽  
Welding Current ◽  
Residual Austenite ◽  
Martensite Phase ◽  
Optical Observations ◽  
Bead Geometry ◽  
Steel Joints

Generally, the quality and properties of a weld joint is strongly influenced by welding variables during process. In order to achieve an ideal weld, it is important attention to bead geometry and microstructure evolution of weld metal. The effect of process variables on penetration and microstructure of C-80 steel joints produced by robotic CO2 arc welding was studied in present work. Different samples were produced by employing arc voltages of 23, 25 and 27 V, welding currents of 100, 110 and 120 A and welding speeds of 42, 62 and 82 cm/min. After welding process, geometric measurements were performed on welding specimens and the microstructural evolutions were investigated by optical observations of the weld cross sections. Results were clearly illustrated that increasing in welding current or arc voltage increases the depth of weld penetration. The highest penetration in this research was observed in 62 cm/min welding speed. The metallographic examinations also indicated that the microstructure of weld metal in all of specimens was composed mainly of martensite (M) and residual austenite (A) phases that a portion of martensite phase had been tempered.

Dependence of Silicon and Manganese Content in the Weld Metal on the Welding Current and Method of Gas Shielding

2015 ◽  
Vol 756 ◽  
pp. 92-96 ◽  
Author(s):  
Dmitry A. Chinakhov
Keyword(s):  
Chemical Composition ◽  
Weld Metal ◽  
Gas Dynamics ◽  
Gas Flow ◽  
Manganese Content ◽  
Welding Current ◽  
Mag Welding ◽  
Different Types ◽  
Considerable Impact ◽  
Electrode Metal

The influence of the welding current and method of gas shielding in MAG welding on the content of silicon and manganese is considered. Results of study of the welded specimens of steels 45 and 30HGSA when applying welding wire of different formulas and different types of gas shielding (traditional shielding and two-jet shielding) are given. It is established that in MAG welding the value of the welding current and the speed of the gas flow from the welding nozzle have a considerable impact on the chemical composition of the weld metal. The consumable electrode welding under double-jet gas shielding provides the directed gas-dynamics in the welding area and enables controlling the electrode metal transfer and the chemical composition of a weld.

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